While it is difficult to repair holes and ripped seams in leather jackets by hand, there are some tricks to this kind of repair. You can also use a sewing machine if you have one. Keep in mind that you want the best possible repair for your jacket and that you have several options for caring for it when there are holes.
Use tweezers or a scalpel to remove any stray threads that need to be cleared away from the hole in your jacket.
Use a sewing machine to repair stitching in ripped seams.
Use a clear, strong glue and a patch over a hole if it's not in the seam and if the leather is too thick to sew by hand. If the leather is thin enough in the area around the hole, sew the patch on it on the inside, using a thick needle and beeswax thread.
Use a liquid leather repair kit to repair the hole, following the instructions on the box it came in. These repair kits can be purchased on the Internet.
Take your leather jacket to your neighborhood tailor if you are unable to repair it yourself.